Semiconductor device and method for forming the same

ABSTRACT

Semiconductor devices and a method for forming the same are provided. In various embodiments, a method for forming a semiconductor device includes receiving a semiconductor substrate including a channel. An atmosphere-modulation layer is formed over the channel. An annealing process is performed to form an interfacial layer between the channel and the atmosphere-modulation layer.

BACKGROUND

Various thermal treatments are performed on a semiconductor wafer toachieve effective reaction with the interface and the semiconductorwafer while forming a semiconductor device. As the dimensions of thesemiconductor device scaled down, the complexity of processing andmanufacturing the semiconductor device has been increased due to limitedthermal budget requirement, which is related to the processing time andthe temperature of the thermal treatments. From the viewpoint ofreliability of the semiconductor device, the thermal treatment withhigh-temperature is favorable. However, such thermal treatment has to beperformed within a short time due to limited thermal budget, which maylead to poor semiconductor device performance. Accordingly, the methodfor forming the semiconductor device has to be continuously improved soas to obtain a more satisfactory semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A through 1C are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 2A through 2C are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 3A through 3D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 4A through 4D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 5A through 5D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 6A through 6D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 7A through 7D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

FIGS. 8A through 8D are cross-sectional views at various stages offorming a semiconductor device in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” “top,” “bottom,” and the like, may be used herein forease of description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

As aforementioned, it becomes more challenging for forming asemiconductor device as the dimensions are further scaled down. Forinstance, optimization of post high-k (HK) annealing is essential togate stack performance, such as gate leakage, equivalent oxide thickness(EOT) or capacitance equivalent thickness (CET), mobility, and drivingcurrent. Moreover, reliability is also strongly affected by post-HKannealing. Generally, an annealing process usually requires hightemperature considering the reliability. However, the annealing durationhas to be controlled in a short period to prevent thick CET. This wouldresult in poor uniformity and/or strain relaxation of the semiconductordevice. Therefore, the method for forming a semiconductor device iscontinually required to be improved.

In order to solve the above-mentioned problems, the present disclosureprovides semiconductor devices and a method for forming the same, whichapply an atmosphere-modulation layer that is beneficial forhigh-pressure annealing with low-thermal budget. Therefore, theuniformity of interfaces in the semiconductor devices can be improved,and the strain from the process-induced stressor can be reserved.

FIGS. 1A through 1C are cross-sectional views at various stages offorming a semiconductor device 100 in accordance with some embodiments.

Referring to FIG. 1A, a semiconductor substrate 110 is received, and thesemiconductor substrate 110 includes channels 112. Anatmosphere-modulation layer 130 is formed over the channels 112.

In some embodiments, the semiconductor substrate 110 is a bulk substrateor a semiconductor-on-insulator (SOI) substrate. Examples of thematerial of the semiconductor substrate 110 include but are not limitedto pure silicon, pure germanium, a Group IV compound, a Group III-Vcompound, and a combination thereof. The Group IV compound may besilicon carbide (SiC), silicon germanium (SiGe), or a combinationthereof. The Group III-V compound may be GaN, GaP, GaAs, GaSb, AlN, AlP,AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb,AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb,GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb,GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or acombination thereof.

The channels 112 are disposed between a source electrode (not shown) anda drain electrode (not shown) for current flowing from the drainelectrode to the source electrode or from the source electrode to thedrain electrode. In some embodiments, the channels 112 protrude from thesemiconductor substrate 110 as shown in FIG. 1A. That is, the channels112 may be referred as fin structures, and the formed semiconductordevice 100 may be a fin-like field-effect transistor (FinFET). Thechannels (or the fin structures) 112 may be formed by any suitableprocesses, such as photolithography and etching. The photolithographymay include forming a photoresist layer (not shown) over thesemiconductor substrate 110, exposing the photoresist layer to form apattern, performing post-exposure bake processes, and developing thepattern to form a photoresist mask. The aforementioned photoresist maskis used to protect portions of the semiconductor substrate 110 whileforming trenches in the semiconductor substrate 110 by the etchingprocess, to form the channels 112.

The semiconductor substrate 110 and the channels 112 may be made of thesame or different materials. In some embodiments, the semiconductorsubstrate 110 and the channels 112 are integrally formed, which there isno boundary between the semiconductor substrate 110 and the channels112.

As shown in FIG. 1A, isolation structures 120 may be formed in thesemiconductor substrate 110, and between two adjacent channels 112. Insome embodiments, the isolation structures 120 are shallow trenchisolation (STI) structures. The isolation structures 120 are configuredto separate the two channels 112. The isolation structures 120 may bemade of a dielectric material. Examples of the dielectric materialincludes but are not limited to silicon oxide, silicon nitride, siliconoxynitride, fluoride-doped silicate glass, a low-k dielectric material,and a combination thereof. The isolation structures 120 may be formed byany suitable technique. For instance, the material of the isolationstructures 120 is deposited over the semiconductor substrate 110. Then,an upper portion of the isolation structure material is removed, therebyforming the isolation structures 120 between the channels 112. Theisolation structure material may be deposited by chemical vapordeposition (CVD), plasma enhanced chemical vapor deposition (PECVD),low-pressure chemical vapor deposition (LPCVD), high-pressure chemicalvapor deposition (HPCVD), or the like. The upper portion of theisolation structure material may be removed by chemical-mechanicalpolishing (CMP) and/or etching.

In some embodiments, the atmosphere-modulation layer 130 has a thicknessin a range from about 5 angstrom (Å) to about 20 Å. Theatmosphere-modulation layer 130 may be made of a material selected fromthe group consisting of metal nitride (e.g., AlN_(x)), oxynitride (e.g.,SiO_(x)N_(y)), and a combination thereof, and may be referred as anitrogen containing layer. In some embodiments, theatmosphere-modulation layer 130 is formed by various nitridation ordeposition processes, such as plasma nitridation or atomic layerdeposition (ALD).

Referring to FIG. 1B, an annealing process is performed, thereby formingan interfacial layer 140 between the channel 112 and theatmosphere-modulation layer 130.

In some embodiments, the annealing process is a high-pressure annealingprocess, and is performed in an oxygen-containing gas. Hence, theatmosphere-modulation layer 130 is used to control the amount of oxygenentering the channels 112 in order to slow down the speed of the oxygenentering the channels 112, and may be referred as an oxygen-modulationlayer. The oxygen-containing gas may include at least one of oxygen(O₂), ozone (O₃), water vapor (H₂O or D₂O), nitric oxide (NO), nitrousoxide (N₂O), and nitrogen dioxide (NO₂). Specifically, high-pressuredeuterium or hydrogen annealing shows benefit to the interface statedensity as well as the reliability, such as hot carrier effect (HCE).

The process pressure for the high-pressure annealing process may lie inbetween about 10 atmospheres (atm) to about 70 atm. The structure may beheated under a temperature of about 200° C. to about 700° C. In someembodiments, the annealing process is performed for about 3 minutes toabout 60 minutes, which is the duration of the structure being heatedunder high pressure.

It is noteworthy that the annealing temperature of the method inaccordance with some embodiments of the present disclosure is lower thanthat of general methods, which is usually over 900° C. Thehigh-temperature annealing used in general methods would not be workablefor the Ge or III-V based materials, because these materials have lowmelting points. Even for the Si-based semiconductor device, there ispotential risk of strain relaxation as annealing temperature iselevated. Accordingly, the method of the present disclosure with lowerannealing temperature is suitable for forming the semiconductor device,especially for the semiconductor device with high-mobility channel suchas Ge-containing and Group III-V based materials. Moreover, the methodof the present disclosure is with low-thermal budget, which effectivelyreserves the strain from the process induced stressor.

Further, the method in accordance with some embodiments of the presentdisclosure has a longer annealing duration than general methods, whichis usually few seconds. A semiconductor device treated by generalmethods with such a short time would result in poor uniformity ofinterfacial layer. Although the uniformity can be improved by a longerannealing duration, this would cause over-thick CET, which isundesirable for semiconductor device. In contrast, the method of thepresent disclosure includes the atmosphere-modulation layer. Theatmosphere-modulation layer 130 is used to control the amount ofatmosphere that is used in the annealing process entering the channels112. That is, the speed of the atmosphere entering the channels 112 canbe slowed down. The atmosphere is blocked in the atmosphere-modulationlayer 130, and the portion of the channels 112 adjacent to theatmosphere-modulation layer 130 is annealed to form the interfaciallayer 140. Hence, the reaction time of the annealing process can beincreased, thereby improving the CET as well as the uniformity of theinterfacial layer 140 and post high-k annealing.

The interfacial layer 140 is formed from the channels 112. In someembodiments, when the annealing process is performed in theoxygen-containing gas, the interfacial layer 140 is formed by oxidationof the channels 112. That is, the material of the interfacial layer 140is oxide of the material of the channels 112. The formed interfaciallayer 140 after the high-pressure annealing process may be a fewÅngström thick, which may be tuned by annealing condition, properties ofthe atmosphere-modulation layer 130, and materials of the semiconductorsubstrate 110. In some embodiments, the interfacial layer 140 has athickness in a range from about 5 Å to about 50 Å.

Referring to FIG. 1C, a gate dielectric layer 150 and a gate electrode160 are formed over the atmosphere-modulation layer 130 to form thesemiconductor device 100.

In some embodiments, the gate dielectric layer 150 is a high-kdielectric layer. As used herein, the term “high-k dielectric” refers tothe material having a dielectric constant, k, greater than about 3.9,which is the k value of SiO₂. The material of the high-k dielectriclayer may be any suitable material. Examples of the material of thehigh-k dielectric layer include but are not limited to Al₂O₃, HfO₂,ZrO₂, La₂O₃, TiO₂, SrTiO₃, LaAlO₃, Y₂O₃, Al₂O_(x)N_(y), HfO_(x)N_(y),ZrO_(x)N_(y), La₂O_(x)N_(y), TiO_(x)N_(y), SrTiO_(x)N_(y),LaAlO_(x)N_(y), Y₂O_(x)N_(y), SiON, SiN_(x), a silicate thereof, and analloy thereof. Each value of x is independently from 0.5 to 3, and eachvalue of y is independently from 0 to 2.

In some embodiments, the gate electrode 160 is made of a material suchas metal, metal alloy, and metal silicide. Examples of the material ofthe metal gate electrode include but are not limited to tungsten (W),titanium (Ti), tantalum (Ta), aluminum (Al), nickel (Ni), ruthenium(Ru), palladium (Pd), platinum (Pt), tungsten nitride (WN_(x)), titaniumnitride (TiN), tantalum nitride (TaN), aluminum nitride (AlN), tungstensilicide (WSi_(x)), nickel silicide (Ni₂Si), titanium silicide (TiSi₂),titanium aluminide (TiAl), an alloy thereof, and a combination thereof.

In some embodiments, the gate dielectric layer 150 and the gateelectrode 160 are formed by deposition, such as chemical vapordeposition (CVD), atmospheric pressure CVD (APCVD), low pressure CVD(LPCVD), plasma enhanced CVD (PECVD), metal-organic CVD (MOCVD),physical vapor deposition (PVD), atomic layer deposition (ALD), chemicalsolution deposition, sputtering, and a combination thereof. In someembodiments, the gate dielectric layer 150 is deposited onto theatmosphere-modulation layer 130 by ALD, and the gate electrode 160 issubsequently deposited.

The formed semiconductor device 100 includes the semiconductor substrate110 that includes the channels (or the fin structures) 112, theinterfacial layer 140, the atmosphere-modulation layer (or thenitrogen-containing layer) 130, the gate dielectric layer 150, and thegate electrode 160. The interfacial layer 140 is over the channels 112.The atmosphere-modulation layer 130 is over the interfacial layer 140.The gate dielectric layer 150 is over the atmosphere-modulation layer130. The gate electrode 160 is over the gate dielectric layer 150.

The method for forming the semiconductor device 100 in accordance withsome embodiments of the present disclosure applies theatmosphere-modulation layer 130 and the high-pressure annealing, whichis an highly integrated and low-thermal budget gate stack process toimprove uniformity of the interfacial layer and strain relaxation.Further, by using the method shown in FIGS. 1A through 1C, both bulkgate dielectric layer/interfacial layer as well as interfaciallayer/semiconductor substrate interface can be passivated in one-stepprocess, which reduces the thermal budget and process cost.

It is noteworthy that the shown in FIGS. 1A through 1C forming methodand the formed structure are examples, and can be applied to all kindsof structures and methods for forming the same. Examples of thestructure include but are not limited to planar MOSFET, SOI MOSFET,FinFET, and nanowire FET.

FIGS. 2A through 2C are cross-sectional views at various stages offorming a semiconductor device 200 in accordance with some embodiments.

Referring to FIG. 2A, a semiconductor substrate 210 is received, and thesemiconductor substrate 210 includes channels 212. Isolation structures220 may be formed in the semiconductor substrate 210, and between twoadjacent channels 212. An initial layer 230 is formed over the channels212, and an atmosphere-modulation layer 240 is formed over the initiallayer 230.

The semiconductor substrate 210 and the channels 212 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

The initial layer 230 is used as a starting material to form aninterfacial layer in the subsequent annealing process. In someembodiments, the initial layer 230 is made of a material selected fromthe group consisting of oxide, silicon, and a combination thereof.Particularly, the material of the initial layer 230 may be native oxide,intentionally formed oxide by process (including deposition, chemicalreaction, or thermal growth), silicon, or a combination thereof. It isnoteworthy that the initial layer 230 is used as a silicon capping layerwhen the channels 212 are not made of pure silicon. The initial layer230 may be formed by any suitable process, such as deposition.

The atmosphere-modulation layer 240 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 240 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.

Other features such as materials and forming manners of thesemiconductor substrate 210, the channels 212, the isolation structures220, and the atmosphere-modulation layer 240 may be referred to thoseexemplified for the counterparts of FIG. 1A.

Referring to FIG. 2B, an annealing process is performed, thereby formingan interfacial layer 250 from the initial layer 230. The formedinterfacial layer 250 is between the initial layer 230 and theatmosphere-modulation layer 240. In some embodiments, when the annealingprocess is performed in the oxygen-containing gas, the interfacial layer250 is formed by oxidation of the initial layer 230. That is, thematerial of the interfacial layer 250 is oxide of the material of theinitial layer 230.

The atmosphere-modulation layer 240 is used to control the amount ofatmosphere that is used in the annealing process entering the initiallayer 230. That is, the speed of the atmosphere entering the initiallayer 230 can be slowed down. The atmosphere is blocked in theatmosphere-modulation layer 240, and the portion of the initial layer230 adjacent to the atmosphere-modulation layer 240 is annealed to formthe interfacial layer 250.

In some embodiments, the annealing process is a high-pressure annealingprocess, and is performed in an oxygen-containing gas. Theoxygen-containing gas may include at least one of O₂, O₃, H₂O, D₂O, NO,N₂O, and NO₂. The process pressure for the high-pressure annealingprocess may lie in between about 10 atm to about 70 atm. The structuremay be heated under a temperature of about 200° C. to about 700° C. forabout 3 minutes to about 60 minutes. Other conditions of the annealingprocess may be referred to those exemplified for the counterparts ofFIG. 1B.

The interfacial layer 250 is formed from the initial layer 230. In someembodiments, when the annealing process is performed in theoxygen-containing gas, the interfacial layer 250 is formed by oxidationof the initial layer 230. That is, the material of the interfacial layer250 is oxide of the material of the initial layer 230. In someembodiments, the interfacial layer 250 has a thickness in a range fromabout 5 Å to about 50 Å, and may be tuned by annealing condition,properties of the atmosphere-modulation layer 240, and materials of thesemiconductor substrate 210.

Referring to FIG. 2C, a gate dielectric layer 260 and a gate electrode270 are formed over the atmosphere-modulation layer 240 to form thesemiconductor device 200. The features such as materials and formingmanners of the gate dielectric layer 260 and a gate electrode 270 may bereferred to those exemplified for the counterparts of FIG. 1C.

The difference between the forming methods shown in FIGS. 2A through 2Cand FIGS. 1A through 1C is that the forming method shown in FIGS. 2Athrough 2C applies the initial layer 230 to form the interfacial layer250, while the forming method shown in FIGS. 1A through 1C uses thechannels 112 to form the interfacial layer 140. This difference does notaffect the functions of other components and steps in the embodiments.Therefore, the semiconductor device 200 and the forming method thereofhave the same functions and advantages as the embodiments shown in FIGS.1A through 1C.

FIGS. 3A through 3D are cross-sectional views at various stages offorming a semiconductor device 300 in accordance with some embodiments.

Referring to FIG. 3A, a semiconductor substrate 310 is received, and thesemiconductor substrate 310 includes channels 312. Isolation structures320 may be formed in the semiconductor substrate 310, and between twoadjacent channels 312. An atmosphere-modulation layer 330 is formed overthe channels 312.

The semiconductor substrate 310 and the channels 312 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

The atmosphere-modulation layer 330 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 330 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 330 may be formed by any suitablenitridation or deposition processes, (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 310, the channels 312, the isolation structures320, and the atmosphere-modulation layer 330 may be referred to thoseexemplified for the counterparts of FIG. 1A.

Referring to FIG. 3B, a gate dielectric layer 340 is formed over theatmosphere-modulation layer 330. In some embodiments, the gatedielectric layer 340 is formed by depositing onto theatmosphere-modulation layer 330. The deposition may be performed by, butnot limited to, ALD. The material of the gate dielectric layer 340 maybe referred to those exemplified for the counterparts of FIG. 1C.

Referring to FIG. 3C, an annealing process is performed, thereby formingan interfacial layer 350 from the channels 312. The formed interfaciallayer 350 is between the channels 312 and the atmosphere-modulationlayer 330.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. Other conditions of the annealing process may bereferred to those exemplified for the counterparts of FIG. 1B.

It is noteworthy that the annealing process is performed afterdepositing the gate dielectric layer 340. In some embodiments, when thegate dielectric layer 340 is made of a high-k dielectric material thatcontaining oxygen, both oxygen-containing and oxygen-free gas may beintroduced into ambient of the annealing process. That is, the annealingprocess may be performed in oxygen-containing gas or oxygen-free gas.The reason that the oxygen-free gas may be used is that the ambient ofthe annealing process would push the oxygen in the gate dielectric layer340 penetrating the atmosphere-modulation layer 330 to react with thechannels 312, thereby forming the interfacial layer 350. Hence, theoxygen for forming the interfacial layer 350 may be originated from theatmosphere used in the annealing process and/or the material of the gatedielectric layer 340. In some embodiments, the oxygen-containing gasincludes at least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and theoxygen-free gas is an inert gas, such as nitrogen (N₂), argon (Ar), anda combination thereof.

When the atmosphere that is used in the annealing process containsoxygen, the atmosphere-modulation layer 330 is used to control theamount of the oxygen in the atmosphere entering the channels 312. Whenthe atmosphere that is used in the annealing process is the oxygen-freegas, the atmosphere-modulation layer 330 is used to control the speed ofthe atmosphere penetrating the atmosphere-modulation layer 330, therebycontrolling the amount of the oxygen in the gate dielectric layer 340entering the channels 312, which the oxygen is pushed by the atmosphere.Accordingly, the speed of the oxygen entering the channels 312 can beslowed down by the atmosphere-modulation layer 330. The oxygen isblocked in the atmosphere-modulation layer 330, and the portion of thechannels 312 adjacent to the atmosphere-modulation layer 330 is annealedto form the interfacial layer 350.

In some embodiments, the interfacial layer 350 is formed by oxidation ofthe channels 312. That is, the material of the interfacial layer 350 isoxide of the material of the channels 312. The formed interfacial layer350 after the high-pressure annealing may be a few Ångström thick (e.g.,about 5 Å to about 50 Å), which may be tuned by annealing condition,properties of the atmosphere-modulation layer 330 and the gatedielectric layer 340, and materials of the semiconductor substrate 310.

Referring to FIG. 3D, a gate electrode 360 is formed over the gatedielectric layer 340 to form the semiconductor device 300. The featuressuch as materials and forming manners of the gate electrode 360 may bereferred to those exemplified for the counterparts of FIG. 1C.

The difference between the forming methods shown in FIGS. 3A through 3Dand FIGS. 1A through 1C is that the annealing process is performed afterthe gate dielectric layer 340 deposition in the forming method shown inFIGS. 3A through 3D. This difference does not affect the functions ofother components and steps in the embodiments. Therefore, thesemiconductor device 300 and the forming method thereof have the samefunctions and advantages as the embodiments shown in FIGS. 1A through1C.

FIGS. 4A through 4D are cross-sectional views at various stages offorming a semiconductor device 400 in accordance with some embodiments.

Referring to FIG. 4A, a semiconductor substrate 410 is received, and thesemiconductor substrate 410 includes channels 412. Isolation structures420 may be formed in the semiconductor substrate 410, and between twoadjacent channels 412. An initial layer 430 is formed over the channels412, and an atmosphere-modulation layer 440 is formed over the initiallayer 430.

The semiconductor substrate 410 and the channels 412 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

In some embodiments, the material of the initial layer 430 is nativeoxide, intentionally formed oxide by process (including deposition,chemical reaction, or thermal growth), silicon, or a combinationthereof.

The atmosphere-modulation layer 440 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 440 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 440 may be formed by any suitablenitridation or deposition processes (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 410, the channels 412, the isolation structures420, and the atmosphere-modulation layer 440 may be referred to thoseexemplified for the counterparts of FIG. 1A. Further, other features ofthe initial layer 430 may be referred to those exemplified for thecounterparts of FIG. 2A.

Referring to FIG. 4B, a gate dielectric layer 450 is formed over theatmosphere-modulation layer 440. In some embodiments, the gatedielectric layer 450 is formed by depositing onto theatmosphere-modulation layer 440. The deposition may be performed by, butnot limited to, ALD. The material of the gate dielectric layer 450 maybe referred to those exemplified for the counterparts of FIG. 1C.

Referring to FIG. 4C, an annealing process is performed, thereby formingan interfacial layer 460 from the initial layer 430. The formedinterfacial layer 460 is between the initial layer 430 and theatmosphere-modulation layer 440.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. The annealing process is performed after depositingthe gate dielectric layer 450. In some embodiments, the gate dielectriclayer 450 is made of a high-k dielectric material that containingoxygen, and the annealing process may be performed in oxygen-containinggas or oxygen-free gas. The ambient of the annealing process would pushthe oxygen in the gate dielectric layer 450 to penetrate theatmosphere-modulation layer 440. A portion of the initial layer 430would be annealed, thereby forming the interfacial layer 460. Hence, theoxygen for forming the interfacial layer 460 may be originated from theatmosphere used in the annealing process and/or the material of the gatedielectric layer 450. In some embodiments, the oxygen-containing gasincludes at least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and theoxygen-free gas is an inert gas, such as nitrogen (N₂), argon (Ar), anda combination thereof. Other conditions of the annealing process may bereferred to those exemplified for the counterparts of FIG. 1B.

The atmosphere-modulation layer 440 is used to control the amount ofatmosphere that is used in the annealing process and/or the oxygen inthe gate dielectric layer 450 entering the initial layer 430. That is,the speed of oxygen entering the initial layer 430 can be slowed down.The oxygen is blocked in the atmosphere-modulation layer 440, and theportion of the initial layer 430 adjacent to the atmosphere-modulationlayer 440 is annealed to form the interfacial layer 460.

In some embodiments, the interfacial layer 460 is formed by oxidation ofthe initial layer 430. That is, the material of the interfacial layer460 is oxide of the material of the initial layer 430. The interfaciallayer 460 has a thickness in a range from about 5 Å to about 50 Å, andmay be tuned by annealing condition, properties of theatmosphere-modulation layer 440, and materials of the semiconductorsubstrate 410.

Referring to FIG. 4D, a gate electrode 470 is formed over the gatedielectric layer 450 to form the semiconductor device 400. The featuressuch as materials and forming manners of the gate electrode 470 may bereferred to those exemplified for the counterparts of FIG. 1C.

The difference between the forming methods shown in FIGS. 4A through 4Dand FIGS. 3A through 3D is that the forming method shown in FIGS. 4Athrough 4D applies the initial layer 430 to form the interfacial layer460, while the forming method shown in FIGS. 3A through 3D uses thechannels 312 to form the interfacial layer 350. This difference does notaffect the functions of other components and steps in the embodiments.Therefore, the semiconductor device 400 and the forming method thereofhave the same functions and advantages as the embodiments shown in FIGS.3A through 3D.

FIGS. 5A through 5D are cross-sectional views at various stages offorming a semiconductor device 500 in accordance with some embodiments.

Referring to FIG. 5A, a semiconductor substrate 510 is received, and thesemiconductor substrate 510 includes channels 512. Isolation structures520 may be formed in the semiconductor substrate 510, and between twoadjacent channels 512. An atmosphere-modulation layer 530 is formed overthe channels 512.

The semiconductor substrate 510 and the channels 512 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

The atmosphere-modulation layer 530 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 530 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 530 may be formed by any suitablenitridation or deposition processes (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 510, the channels 512, the isolation structures520, and the atmosphere-modulation layer 530 may be referred to thoseexemplified for the counterparts of FIG. 1A.

Referring to FIG. 5B, a first gate dielectric layer 542 is formed overthe atmosphere-modulation layer 530. In some embodiments, the first gatedielectric layer 542 is formed by depositing onto theatmosphere-modulation layer 530. The deposition may be performed by, butnot limited to, ALD. The material of the first gate dielectric layer 542may be referred to those exemplified for the counterparts of FIG. 1C.

Referring to FIG. 5C, an annealing process is performed, thereby formingan interfacial layer 550 from the channels 512. The formed interfaciallayer 550 is between the channels 512 and the atmosphere-modulationlayer 530.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. The annealing process is performed after depositingthe first gate dielectric layer 542. In some embodiments, when the firstgate dielectric layer 542 is made of a high-k dielectric material thatcontaining oxygen, both oxygen-containing and oxygen-free gas may beintroduced into ambient of the annealing process. That is, the annealingprocess may be performed in oxygen-containing gas or oxygen-free gas.The oxygen for forming the interfacial layer 550 may be originated fromthe atmosphere used in the annealing process and/or the material of thefirst gate dielectric layer 542. The oxygen-containing gas may includeat least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and the oxygen-freegas may be an inert gas, such as nitrogen (N₂), argon (Ar), and acombination thereof. Other conditions of the annealing process may bereferred to those exemplified for the counterparts of FIG. 1B.

The formed interfacial layer 550 after the high-pressure annealing maybe a few Ångström thick (e.g., about 5 Å to about 50 Å), which may betuned by annealing condition, properties of the atmosphere-modulationlayer 530 and the first gate dielectric layer 542, and materials of thesemiconductor substrate 510.

Referring to FIG. 5D, a second gate dielectric layer 544 and a gateelectrode 560 are formed over the first gate dielectric layer 542 toform the semiconductor device 500. In some embodiments, the second gatedielectric layer 544 is formed by depositing onto the first gatedielectric layer 542. The deposition may be performed by, but notlimited to, ALD. The gate electrode 560 may be subsequently depositedover the second gate dielectric layer 544. Other features such asmaterials and forming manners of the second gate dielectric layer 544and the gate electrode 560 may be referred to those exemplified for thecounterparts of FIG. 1C.

The difference between the forming methods shown in FIGS. 5A through 5Dand FIGS. 3A through 3D is that the forming method shown in FIGS. 5Athrough 5D further includes a step of forming the second gate dielectriclayer 544 before forming the gate electrode 560. This difference doesnot affect the functions and steps of other components in theembodiments. Therefore, the semiconductor device 500 and the formingmethod thereof have the same functions and advantages as the embodimentsshown in FIGS. 3A through 3D.

FIGS. 6A through 6D are cross-sectional views at various stages offorming a semiconductor device 600 in accordance with some embodiments.

Referring to FIG. 6A, a semiconductor substrate 610 is received, and thesemiconductor substrate 610 includes channels 612. Isolation structures620 may be formed in the semiconductor substrate 610, and between twoadjacent channels 612. An initial layer 630 is formed over the channels612, and an atmosphere-modulation layer 640 is formed over the initiallayer 630.

The semiconductor substrate 610 and the channels 612 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

In some embodiments, the material of the initial layer 630 is nativeoxide, intentionally formed oxide by process (including deposition,chemical reaction, or thermal growth), silicon, or a combinationthereof.

The atmosphere-modulation layer 640 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 640 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 640 may be formed by any suitablenitridation or deposition processes (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 610, the channels 612, the isolation structures620, and the atmosphere-modulation layer 640 may be referred to thoseexemplified for the counterparts of FIG. 1A. Further, other features ofthe initial layer 630 may be referred to those exemplified for thecounterparts of FIG. 2A.

Referring to FIG. 6B, a first gate dielectric layer 652 is formed overthe atmosphere-modulation layer 640. In some embodiments, the first gatedielectric layer 652 is formed by depositing onto theatmosphere-modulation layer 640. The deposition may be performed by, butnot limited to, ALD. The material of the first gate dielectric layer 652may be referred to those exemplified for the counterparts of FIG. 1C.

Referring to FIG. 6C, an annealing process is performed, thereby formingan interfacial layer 660 from the initial layer 630. The formedinterfacial layer 660 is between the initial layer 630 and theatmosphere-modulation layer 640.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. The annealing process is performed after depositingthe first gate dielectric layer 652. In some embodiments, when the firstgate dielectric layer 652 is made of a high-k dielectric material thatcontaining oxygen, both oxygen-containing and oxygen-free gas may beintroduced into ambient of the annealing process. That is, the annealingprocess may be performed in oxygen-containing gas or oxygen-free gas.The oxygen for forming the interfacial layer 660 may be originated fromthe atmosphere used in the annealing process and/or the material of thefirst gate dielectric layer 652. The oxygen-containing gas may includeat least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and the oxygen-freegas may be an inert gas, such as nitrogen (N₂), argon (Ar), and acombination thereof. Other conditions of the annealing process may bereferred to those exemplified for the counterparts of FIG. 1B.

The formed interfacial layer 660 after the high-pressure annealing maybe a few Ångström thick (e.g., about 5 Å to about 50 Å), which may betuned by annealing condition, properties of the atmosphere-modulationlayer 630 and the first gate dielectric layer 652, and materials of thesemiconductor substrate 610.

Referring to FIG. 6D, a second gate dielectric layer 654 and a gateelectrode 670 are formed over the first gate dielectric layer 652 toform the semiconductor device 600. In some embodiments, the second gatedielectric layer 654 is formed by depositing onto the first gatedielectric layer 652. The deposition may be performed by, but notlimited to, ALD. The gate electrode 670 may be subsequently depositedover the second gate dielectric layer 654. Other features such asmaterials and forming manners of the second gate dielectric layer 654and the gate electrode 670 may be referred to those exemplified for thecounterparts of FIG. 1C.

The difference between the forming methods shown in FIGS. 6A through 6Dand FIGS. 4A through 4D is that the forming method shown in FIGS. 6Athrough 6D further includes a step of forming the second gate dielectriclayer 654 before forming the gate electrode 670. This difference doesnot affect the functions and steps of other components in theembodiments. Therefore, the semiconductor device 600 and the formingmethod thereof have the same functions and advantages as the embodimentsshown in FIGS. 4A through 4D.

FIGS. 7A through 7D are cross-sectional views at various stages offorming a semiconductor device 700 in accordance with some embodiments.

Referring to FIG. 7A, a semiconductor substrate 710 is received, and thesemiconductor substrate 710 includes channels 712. Isolation structures720 may be formed in the semiconductor substrate 710, and between twoadjacent channels 712. An atmosphere-modulation layer 730 is formed overthe channels 712.

The semiconductor substrate 710 and the channels 712 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

The atmosphere-modulation layer 730 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 730 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 730 may be formed by any suitablenitridation or deposition processes (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 710, the channels 712, the isolation structures720, and the atmosphere-modulation layer 730 may be referred to thoseexemplified for the counterparts of FIG. 1A.

Referring to FIG. 7B, a first gate dielectric layer 742 and a secondgate dielectric layer 744 are formed over the atmosphere-modulationlayer 730. In some embodiments, the first gate dielectric layer 742 isformed by depositing onto the atmosphere-modulation layer 730, and thesecond gate dielectric layer 744 is formed by depositing onto the firstgate dielectric layer 742. The deposition may be performed by, but notlimited to, ALD. The materials of the first gate dielectric layer 742and the second gate dielectric layer 744 may be referred to thoseexemplified for the counterparts of FIG. 1C.

Referring to FIG. 7C, an annealing process is performed, thereby formingan interfacial layer 750 from the channels 712. The formed interfaciallayer 750 is between the channels 712 and the atmosphere-modulationlayer 730.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. The annealing process is performed after depositingthe first gate dielectric layer 742 and the second gate dielectric layer744. In some embodiments, when the first gate dielectric layer 742and/or the second gate dielectric layer 744 is made of a high-kdielectric material that containing oxygen, both oxygen-containing andoxygen-free gas may be introduced into ambient of the annealing process.That is, the annealing process may be performed in oxygen-containing gasor oxygen-free gas. The oxygen for forming the interfacial layer 750 maybe originated from the atmosphere used in the annealing process and/orat least one of the materials of the first gate dielectric layer 742 andthe second gate dielectric layer 744. The oxygen-containing gas mayinclude at least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and theoxygen-free gas may be an inert gas, such as nitrogen (N₂), argon (Ar),and a combination thereof. Other conditions of the annealing process maybe referred to those exemplified for the counterparts of FIG. 1B.

The formed interfacial layer 750 after the high-pressure annealing maybe a few Ångström thick (e.g., about 5 Å to about 50 Å), which may betuned by annealing condition, properties of the atmosphere-modulationlayer 730, the first gate dielectric layer 742, and the second gatedielectric layer 744, and materials of the semiconductor substrate 710.

Referring to FIG. 7D, a gate electrode 760 is formed over the secondgate dielectric layer 744 to form the semiconductor device 700. The gateelectrode 760 may be formed by deposition. Other features such asmaterials and forming manners of the gate electrode 760 may be referredto those exemplified for the counterparts of FIG. 1C.

The embodiments shown in FIG. 7A through 7D describe a bi-layered gatedielectric structure (i.e., the first gate dielectric layer 742 and thesecond gate dielectric layer 744). In some other embodiments, the methodcan be extended to a multi-layered gate dielectric structure. The gateelectrode may be subsequently formed over the outmost gate dielectriclayer.

The difference between the forming methods shown in FIGS. 7A through 7Dand FIGS. 3A through 3D is that the forming method shown in FIGS. 7Athrough 7D applies bi-layered gate dielectric structure, which furtherincludes a step of forming the second gate dielectric layer 744 beforeperforming the annealing process. This difference does not affect thefunctions and steps of other components in the embodiments. Therefore,the semiconductor device 700 and the forming method thereof have thesame functions and advantages as the embodiments shown in FIGS. 3Athrough 3D.

FIGS. 8A through 8D are cross-sectional views at various stages offorming a semiconductor device 800 in accordance with some embodiments.

Referring to FIG. 8A, a semiconductor substrate 810 is received, and thesemiconductor substrate 810 includes channels 812. Isolation structures820 may be formed in the semiconductor substrate 810, and between twoadjacent channels 812. An initial layer 830 is formed over the channels812, and an atmosphere-modulation layer 840 is formed over the initiallayer 830.

The semiconductor substrate 810 and the channels 812 may be made of thesame or different materials, which may be independently selected fromthe group consisting of pure silicon, pure germanium, a Group IVcompound, a Group III-V compound, and a combination thereof.

In some embodiments, the material of the initial layer 830 is nativeoxide, intentionally formed oxide by process (including deposition,chemical reaction, or thermal growth), silicon, or a combinationthereof.

The atmosphere-modulation layer 840 has a thickness in a range fromabout 5 Å to about 20 Å. The atmosphere-modulation layer 840 may be madeof a material selected from the group consisting of metal nitride (e.g.,AlN_(x)), oxynitride (e.g., SiO_(x)N_(y)), and a combination thereof.The atmosphere-modulation layer 840 may be formed by any suitablenitridation or deposition processes (e.g., plasma nitridation or ALD).

Other features such as materials and forming manners of thesemiconductor substrate 810, the channels 812, the isolation structures820, and the atmosphere-modulation layer 840 may be referred to thoseexemplified for the counterparts of FIG. 1A. Further, other features ofthe initial layer 830 may be referred to those exemplified for thecounterparts of FIG. 2A.

Referring to FIG. 6B, a first gate dielectric layer 852 and a secondgate dielectric layer 854 are formed over the atmosphere-modulationlayer 840. In some embodiments, the first gate dielectric layer 852 isformed by depositing onto the atmosphere-modulation layer 840, and thesecond gate dielectric layer 854 is formed by depositing onto the firstgate dielectric layer 852. The deposition may be performed by, but notlimited to, ALD. The materials of the first gate dielectric layer 852and the second gate dielectric layer 854 may be referred to thoseexemplified for the counterparts of FIG. 1C.

Referring to FIG. 8C, an annealing process is performed, thereby formingan interfacial layer 860 from the initial layer 830. The formedinterfacial layer 860 is between the initial layer 830 and theatmosphere-modulation layer 840.

The process pressure for the high-pressure annealing process may lie inbetween about 10 atm to about 70 atm. The structure may be heated undera temperature of about 200° C. to about 700° C. for about 3 minutes toabout 60 minutes. The annealing process is performed after depositingthe first gate dielectric layer 852 and the second gate dielectric layer854. In some embodiments, when the first gate dielectric layer 852and/or the second gate dielectric layer 854 is made of a high-kdielectric material that containing oxygen, both oxygen-containing andoxygen-free gas may be introduced into ambient of the annealing process.That is, the annealing process may be performed in oxygen-containing gasor oxygen-free gas. The oxygen for forming the interfacial layer 860 maybe originated from the atmosphere used in the annealing process and/orat least one of the materials of the first gate dielectric layer 852 andthe second gate dielectric layer 854. The oxygen-containing gas mayinclude at least one of O₂, O₃, H₂O, D₂O, NO, N₂O, and NO₂, and theoxygen-free gas may be an inert gas, such as nitrogen (N₂), argon (Ar),and a combination thereof. Other conditions of the annealing process maybe referred to those exemplified for the counterparts of FIG. 1B.

The formed interfacial layer 860 after the high-pressure annealing maybe a few Ångström thick (e.g., about 5 Å to about 50 Å), which may betuned by annealing condition, properties of the atmosphere-modulationlayer 840, the first gate dielectric layer 852, and the second gatedielectric layer 854, and materials of the semiconductor substrate 810.

Referring to FIG. 8D, a gate electrode 870 is formed over the secondgate dielectric layer 854 to form the semiconductor device 800. The gateelectrode 870 may be formed by deposition. Other features such asmaterials and forming manners of the gate electrode 870 may be referredto those exemplified for the counterparts of FIG. 1C.

The embodiments shown in FIG. 8A through 8D describe a bi-layered gatedielectric structure (i.e., the first gate dielectric layer 852 and thesecond gate dielectric layer 854). In some other embodiments, the methodcan be extended to a multi-layered gate dielectric structure. The gateelectrode may be subsequently formed over the outmost gate dielectriclayer.

The difference between the forming methods shown in FIGS. 8A through 8Dand FIGS. 4A through 4D is that the forming method shown in FIGS. 8Athrough 8D applies bi-layered gate dielectric structure, which furtherincludes a step of forming the second gate dielectric layer 854 beforeperforming the annealing process. This difference does not affect thefunctions of other components and steps in the embodiments. Therefore,the semiconductor device 800 and the forming method thereof have thesame functions and advantages as the embodiments shown in FIGS. 4Athrough 4D.

The embodiments of the present disclosure discussed above haveadvantages over existing methods and systems. The method for forming thesemiconductor device is a highly integrated, low-thermal budget gatestack process, which applies the atmosphere-modulation layer, therebyimproving the uniformity of the interfacial layer and strain relaxation.Further, the method offers one-step passivation strategy for gatedielectric layer/interfacial layer and interfacial layer/semiconductorsubstrate interfaces. That is, the method combines the passivations ofboth gate dielectric layer/interfacial layer and interfaciallayer/semiconductor substrate into one-step process, which is costsaving. The method retains low-thermal budget during process and lessstrain relaxation, and is suitable for high-mobility channel such asGe-containing and Group III-V based materials. It is understood,however, that other embodiments may have different advantages, and thatno particular advantages is required for all embodiments.

In accordance with some embodiments of the present disclosure, a methodfor forming a semiconductor device includes receiving a semiconductorsubstrate including a channel. An atmosphere-modulation layer is formedover the channel. An annealing process is performed to form aninterfacial layer between the channel and the atmosphere-modulationlayer.

In accordance with other embodiments of the present disclosure, asemiconductor device includes a semiconductor substrate including achannel, an interfacial layer, and an atmosphere-modulation layer. Theinterfacial layer is over the channel. The atmosphere-modulation layeris over the interfacial layer.

In accordance with yet other embodiments of the present disclosure, asemiconductor device includes a semiconductor substrate, a finstructure, an interfacial layer, and a nitrogen-containing layer. Thefin structure is over the semiconductor substrate. The interfacial layeris over the fin structure. The nitrogen-containing layer is over theinterfacial layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a semiconductor device, themethod comprising: receiving a semiconductor substrate comprising achannel protruding from the semiconductor substrate; forming anatmosphere-modulation layer over the channel, wherein theatmosphere-modulation layer is made of a material selected from thegroup consisting of: metal nitride, oxynitride, and a combinationthereof; depositing a first gate dielectric layer over theatmosphere-modulation layer; performing an annealing process to form aninterfacial layer between the channel and the atmosphere-modulationlayer; and after performing the annealing process, depositing a secondgate dielectric layer over the first gate dielectric layer.
 2. Themethod of claim 1, wherein forming the atmosphere-modulation layer isperformed by a nitridation process or a deposition process.
 3. Themethod of claim 1, wherein the annealing process is performed in anoxygen-containing gas.
 4. The method of claim 1, wherein the annealingprocess is performed in an oxygen-containing gas or an oxygen-free gas.5. The method of claim 4, wherein the oxygen-free gas is an inert gas.6. The method of claim 1, wherein the interfacial layer is formed byoxidation of the channel.
 7. The method of claim 1, wherein theinterfacial layer is formed from the channel.
 8. The method of claim 1,further comprising forming an initial layer over the channel.
 9. Themethod of claim 8, wherein the interfacial layer is formed from theinitial layer.
 10. The method of claim 1, wherein the annealing processis performed in an oxygen-free gas.
 11. A semiconductor device,comprising: a semiconductor substrate comprising a channel structurethat comprises a semiconductor channel material; an isolation structureover the semiconductor substrate; an interfacial layer covering over thechannel structure; an atmosphere-modulation layer disposed over theinterfacial layer, wherein the atmosphere-modulation layer is in contactwith the isolation structure and is made of metal nitride; and a gatedielectric layer disposed over the atmosphere-modulation layer and incontact with the isolation structure.
 12. The semiconductor device ofclaim 11, wherein the interfacial layer has a thickness in a range fromabout 5 Å to about 50 Å.
 13. The semiconductor device of claim 11,wherein the atmosphere-modulation layer has a thickness in a range fromabout 5 Å to about 20 Å.
 14. The semiconductor device of claim 11,wherein the isolation structure includes a trench-defining wall thatdefines a trench, and the interfacial layer is in the trench and is incontact with the trench-defining wall.
 15. The semiconductor device ofclaim 11, wherein the interfacial layer has a top surface above a bottomsurface of the atmosphere-modulation layer.
 16. A semiconductor device,comprising: a semiconductor substrate; a channel protruding from thesemiconductor substrate; an interfacial layer over the channel; anitrogen-containing layer over the interfacial layer, wherein thenitrogen-containing layer has a shorter length than the interfaciallayer and is made of oxynitride; and a gate dielectric layer disposedover the nitrogen-containing layer, wherein the nitrogen-containinglayer covers the interfacial layer to separate the interfacial layerfrom the gate dielectric layer.
 17. The semiconductor device of claim16, wherein the interfacial layer has a thickness in a range from about5 Å to about 50 Å.
 18. The semiconductor device of claim 16, wherein thenitrogen-containing layer has a thickness in a range from about 5 Å toabout 20 Å.
 19. The semiconductor device of claim 16, further comprisingan isolation structure over the semiconductor substrate, wherein theisolation structure includes a trench-defining wall that defines atrench, and the interfacial layer is in the trench and is in contactwith the trench-defining wall.
 20. The semiconductor device of claim 16,wherein the interfacial layer has a top surface above a bottom surfaceof the nitrogen-containing layer.